Key Facts

Delirium is an acute confusional state caused by an underlying medical condition. It is a medical emergency requiring urgent investigation and treatment of the cause. It is frequently underdiagnosed, especially the hypoactive subtype.

Epidemiology

Affects 20-30% of medical inpatients aged >65; up to 50% of surgical patients; 80% of ICU patients. More common in those with pre-existing dementia (delirium superimposed on dementia). Hypoactive delirium accounts for ~50% of cases but is frequently missed.

Aetiology

Predisposing factors (vulnerability):

• Advanced age, pre-existing dementia, frailty, sensory impairment, polypharmacy, dehydration, immobility

Precipitating factors (triggers):

• Infection (UTI, pneumonia — most common), pain, constipation, urinary retention
• Drugs: Opioids, anticholinergics, benzodiazepines, steroids, alcohol withdrawal
• Metabolic: Electrolyte disturbance, hypoglycaemia, hypoxia, hepatic/renal failure
• Intracranial: Stroke, SDH, meningitis, seizures
• Cardiac: MI, heart failure, arrhythmia
• Surgery: Post-operative delirium (especially hip fracture, cardiac surgery)

Pathophysiology

• Neuroinflammation: Systemic inflammation → blood-brain barrier disruption → neuroinflammation
• Cholinergic deficit: Anticholinergic drugs worsen delirium; basis for avoiding anticholinergics in elderly
• Dopamine excess: Relative to acetylcholine — basis for antipsychotic use when medication needed
• Cortisol elevation: Stress-induced HPA axis activation
• Disrupted circadian rhythms: Melatonin dysregulation → sleep-wake disturbance

Core Features

• Acute onset (hours to days) — key distinguishing feature
• Fluctuating course — symptoms wax and wane, often worse at night ('sundowning')
• Inattention — cardinal feature; cannot maintain focus, easily distractible
• Altered level of consciousness — ranges from hyperalert to drowsy/stuporous
• Cognitive disturbance — disorientation (time > place > person), memory impairment, disorganised thinking
• Perceptual disturbance — visual hallucinations, illusions, misidentifications

Subtypes

• Hyperactive (~25%): Agitation, restlessness, aggression, hallucinations — easily recognised
• Hypoactive (~50%): Withdrawal, drowsiness, reduced activity — frequently missed, often misdiagnosed as depression
• Mixed (~25%): Features of both

Red Flags

• Acute confusion in elderly — always assume delirium until proven otherwise
• Fever + confusion — sepsis screen urgently
• Head injury + confusion — CT head
• Alcohol history + tremor/agitation — alcohol withdrawal (Wernicke's, DTs)
• New focal neurology — stroke/intracranial pathology

Bedside

• 4AT: Rapid screening (Alertness, AMT4, Attention, Acute change); score ≥4 = likely delirium
• SQiD: Single Question in Delirium ('Is this patient more confused than before?')
• Observations: Temperature, HR, BP, RR, SpO2, glucose — NEWS2 score
• Urinalysis: UTI screening
• Medication review: Identify precipitating drugs

Bloods

• FBC, CRP: Infection markers
• U&Es: Electrolyte disturbance, renal failure
• LFTs: Hepatic encephalopathy
• Calcium, glucose: Metabolic causes
• TFTs, B12: If not recently checked
• Blood cultures: If sepsis suspected
• Blood gas: Hypoxia, hypercapnia

Imaging

• CXR: Pneumonia, heart failure
• CT head: If head injury, focal neurology, or no clear cause identified

Special Tests

• LP: If meningitis/encephalitis suspected (fever, neck stiffness, photophobia)
• EEG: If non-convulsive status epilepticus suspected (generalised slowing in delirium)
• Ammonia: If hepatic encephalopathy suspected

Non-pharmacological (NICE CG103 — always first-line)

• Identify and treat underlying cause — the MOST important intervention
• Reorientation: Clock, calendar, familiar objects, consistent staff
• Communication: Clear, simple, calm, with reassurance
• Optimise environment: Adequate lighting, reduce noise, single room if possible
• Maintain sleep-wake cycle: Daytime natural light, reduce night-time disturbance
• Ensure sensory aids: Glasses, hearing aids
• Mobilise early: Reduce immobility-related complications
• Hydration and nutrition: Ensure adequate oral intake, IV fluids if needed
• Avoid restraint: Physical and chemical restraint should be last resort

Pharmacological (NICE CG103 — only if severe distress/risk to self or others)

• Haloperidol 0.5-1mg PO/IM (lowest effective dose, max 5mg/day) — first-line if medication needed
• Avoid in Lewy body dementia and Parkinson's — use lorazepam 0.5-1mg instead
• Lorazepam 0.5-1mg PO/IM: Preferred in alcohol withdrawal, Lewy body dementia, Parkinson's
• Review and discontinue as soon as delirium resolves
• Stop/reduce precipitating medications (anticholinergics, opioids, benzodiazepines)

Referral Criteria

• Refractory delirium — old age psychiatry/liaison psychiatry
• New cognitive impairment persisting after delirium — memory assessment service (6-12 weeks post-delirium)
• Alcohol withdrawal delirium — addiction services
• Complex medical causes — appropriate specialty

• In-hospital mortality: 10-26% (higher than similar patients without delirium)
• 1-year mortality: Up to 35%
• Cognitive outcomes: ~40% of patients do not return to baseline cognitive function
• Incident dementia: Delirium is an independent risk factor for developing new dementia (OR ~8-12× in next 3 years)
• Hospital stay: Delirium increases length of stay by ~7-10 days
• Prevention: Multicomponent interventions (Hospital Elder Life Program/HELP) reduce delirium incidence by 30-40%
• Hypoactive delirium has worse prognosis than hyperactive

4AT Screening Tool

Delirium vs Dementia